In pressurized medium systems, a load is controlled by using actuators with working chambers having an effective area, on which the pressure of the pressurized medium is effective and causes a force that is, via the actuator, effective on the load. The magnitude of the force is dependent on both the pressurized effective area and the pressure which is, in conventional pressurized medium systems, controlled to produce variable forces. Typical examples include the transferring, lifting and lowering of a load, and the load may, in is physical form, vary from one system to another, being, for example, a part of a structure, an apparatus or a system, to be moved. The pressure control is normally based on adjustment with a loss, an in conventional resistance controlled solutions, the force control of the actuator is achieved by controlling the pressures of the working chambers in a stepless manner. Thus, the pressures are controlled by throttling the flows of pressurized medium entering and exiting the chamber. The control is implemented, for example, by means of proportional valves.
Typically, conventional systems have a pressure side, where the pressure is adjusted and which produces a volume flow of the pressurized medium, and a return side, which is capable of receiving the volume flow and where the prevailing pressure level is as low as possible, a so-called tank pressure, to minimize losses.
Known pressurized media include, for example, hydraulic oil, compressed air and water or water-based hydraulic fluids. The type of the pressurized medium is not limited, but it may vary according to the needs of the application and the requirements set.
Problems with conventional systems include susceptibility to failures and energy losses, particularly losses of hydraulic power and failures in control valves.